Image resolution

It's all about picture elements (pixels), and how many there are per inch.

IMAGES CAN HAVE DIFFERENT SIZES IN EACH FORMAT

The resolution setting controls of a digital camera allow you to determine not only the format (JPEG, TIFF or RAW) but also the size, or resolution, of the picture. Resolution is one of three items that determine the sharpness of your digital images. The other two are the size of your camera's sensor and the quality of your camera's lens.

Note: Not all of these formats, particularly TIFF and RAW, are available with all digital cameras. Most cameras record images only as JPEGs.

What is resolution, anyway?

A digital image is a "bitmap," a picture that is an arrangement of tiny squares of different colors, called pixels. (The name "pixels" is derived from Picture Elements). Resolution refers to the number of pixels that make up a picture. The number of pixels determines image size. Think of a mosaic that is made up of a number of small, different-colored tiles, placed next to each other. When viewed up close, they look like so many small squares, but when viewed from a distance, they coalesce to form a picture or a graphic design. Pixels are the digital equivalent of the little mosaic tiles arranged to make a picture.

THE GREATER THE QUANTITY, THE GREATER THE QUALITY

The quantity of these pixels determines the quality of the image. The number of pixels contained in an inch of the image (known as "ppi," or pixels per inch) is called the image's resolution. When we say an image has a resolution of 72 ppi, it means there are 72 pixels per inch making up the image.

The higher the resolution (that is, the more pixels it has), the greater the picture's detail, and the larger you can print it and still retain sharpness and image quality. (You may wish to have a quick look at Digital cameras - how they work where we touched on the basics of pixels and resolution, before reading on.)

WHAT RESOLUTION SHOULD I SET IN MY CAMERA FOR THE PICTURES I AM GOING TO TAKE?

Most digital cameras give you options for setting the quality of the pictures you are about to take so you can choose the resolution that is best for your intended use of the pictures. For instance, if you are taking pictures of an item that you intend to sell on the internet or a picture destined only to be included in an email, you would use a low resolution. Why? Because you don't need a higher resolution for your picture to appear sharp and clear on the world wide web. But, if you wish to make an enlargement of an image - a big print - you should select a high resolution for the best image quality. If you don't, the enlargement will not appear to be sharp with sufficient detail (it will appear "grainy,") and, worse, you usually won't have a second chance to go back and reshoot the picture at a higher resolution.

The majority of digital cameras store images as JPEGs, which can be compressed for storing in a variety of quality levels, generally three or four, depending upon your camera. JPEG storage options give you great flexibility in deciding whether you want small image files that lack in detail or varying degrees of larger files that retain most of the data in your image. These options may be called Standard, Fine, Extra Fine or Super Fine, with no precise definition for each level. Each camera manufacturer may have a different quality standard for a given level. Extra Fine for one camera may be equivalent to Fine for another, or Super Fine for yet another. To further complicate matters, some cameras save images as TIFF files when you have selected a Super fine resolution setting, and others may use the terms Good or Basic instead of Standard.

If sharpness and image quality are your main concerns, you would be well-advised to use the highest JPEG setting whenever you shoot. A wedding photographer, for example, who may be called upon to provide big enlargements of any of the pictures from the event, should make sure his or her camera is set to Super Fine or the best quality setting provided in the camera.

Bear in mind, though, that a Super Fine setting means large image files, and large image files take up large amounts of storage space, so you would be wise when choosing this option to ensure you have sufficient high-capacity storage media - enough to see you through a full day's shooting of many pictures.

Another consideration in resolution selection is cropping. If you think you will need only a small part of an image - for example, when you just can't get close enough to your subject - you will need to crop the original image. If the original, uncropped picture is photographed at too low a resolution, the cropped portion may not have sufficient detail and will be disappointing and perhaps unusable. When possible, you should avoid having to crop a picture you take by moving in close to fill the frame with your subject, and employing your composition skills to ensure the image has all the elements needed so that it can be displayed uncropped.

If your camera has continuous shooting capabilities, permitting you to rapidly shoot a series of pictures, the resolution setting you select may affect the frame rate at which you can shoot. The delay is caused by your camera's ability (or inability) to quickly store high-resolution pictures.

Some cameras, especially high-quality dSLR's that have a memory buffer for temporary storage, are less affected by image resolution when storing Fine or Super-fine quality JPEG pictures, however their frame rate will be decreased when the memory buffer has filled, or when shooting and storing a high-speed series of large TIFF or RAW image files.

Selecting a lower resolution (Fine instead of Super-fine, for example) will permit high speed continuous shooting at a faster frame rate. Just be sure to select a resolution that is not too low for your intended use of the pictures. It won't matter how quickly you can shoot a series of pictures if you won't be happy with their quality.